Wire testing apparatus



Jan. 4, 1944. R L READING 2,338,202

WIRE TESTING APPARATUS Fild Jan. 6, 1941 4 Sheets-Sheet 1 l I l l l lWSW-3.1, Pmf/ L @www A o ZK/1242 Jan. 4, 1944. R L. READING 2,338,202

WIRE TESTING APPARATUS Filed Jan. v6, 1941 4 Sheets-Sheet 2 Jan. 4,1944. R, L EADWG 2,338,202

WIRE TESTING APPARATUS Filed Jan. 6, 1941 4 Sheets-Sheet 3 WW' uw Jan.4, 1944.

R. l.. READING WIRE TESTING APPARATUS Filed Jap. 6, 1941 4-SheetS-Shee1;4

Wire.

Patented Jan. 4, 1944 WIRE TESTING APPARATUS Raymond L. Reading,Maywood, Ill., assigner to Belden Manufacturing Company, Chicago, Ill.,

a corporation of Illinois Application January 6, 1941, Serial No.373,237

(Cl. i3-5l) 4 Claims.

My invention relates generally to an improved method of, and device for,testing the softness of wire for winding purposes, and it has particularrelation to a testing method and device which involves the measurementof the amount of unwinding or spring-back of a sample piece of wire froma mandrel, and the interpretation of such measurement to determine thewindability of the wire tested.

Electrical manufacturers who purchase large quantities of wire to beused in Winding electrical parts such as cores, coils, etc. are muchconcerned with the winding properties of wire used for these purposes. Aspringy wire is ordinarily hard to wind and therefore undesirable. Onthe other hand, the softer and less resilient a wire is, the better itis suited for making the wound parts of electrical devices.

The method now generally used to determine the softness or windabilityspecifications of wire consists in measuring the percent elongationexhibited by sample pieces of wire. However, this test based onelongation and tensile strength determinations is only partiallysatisfactory, because it does not give an accurate indication of thewindability of the wire as actually used. For example, a number 18 A. W.G. bare copper wire annealed at 900 F. will produce an extremely softwire, but one which will exhibit some tendency to be springy. Now, ifthis same wire is annealed at r150" F., it might easily be more than11/2 times as springy as before, and yet, if the two wires were testedby the percent of elongation method for comparative softness, they wouldbe classied alike, or at least very close together.

The principal object and purpose of my invention is to provide a deviceand method of testing the softness of wire for winding purposes wherebya very close and accurate indication of the windability of the Wire inactual use is obtained. The improved accuracy of my softness testdepends largely upon the fact that actual windings are closely simulatedin making the tests. Furthermore, the invention is very practical andthe testing devices embodying the invention are inexpensive, simple andrugged, and may be easily supplied in large numbers. Likewise, thetechnique of testing wire according to the invention is simple, rapid,and readily acquired.

When a piece of wire is wound around a mandrel with one end held at apoint thereon, the other end will spring back or unwind from the mandrelwhen loosened or freed, to an extent depending upon the springiness orsoftness of the The path or loci of points thus taken by the free endsof pieces of wire ofdiiferent softness follows along a definitemathematical curve. Employing this phenomenon, scales or dialscalibrated for diiferent sized mandrels are made up, which may be usedfor testing the softness of wire of various sizes. 'I'he testing devicesembodied in my invention comprise different arrangements of mandrels andassociated dials or scales, as will appear hereinafter.

For a more complete understanding of the nature and scope of myinvention, reference may now be had to the following detaileddescription taken in connection with the accompanying drawings, inwhich:

Figs. l, 2, 3, 4A, and 4B are mathematical diagrams by which theprinciples of my invention may be explained;

Fig. 5 is a front elevational view of one form of testing deviceembodying the Apresentinvention;

Fig. 6 is a vertical sectional View taken on line (5 6 of Fig. 5;

Fig. 7 is a sectional view taken on line 1 1 of Fig. 6;

Fig. 8 is a diagrammatic View showing the manner in which a test sampleof wire is placed on the testing device; and

Fig. 9 is a perspective view showing how the softness or springinessreading for a piece of wire is obtained or determined on the wiretesting den vice.

A complete understanding of my invention re quires a somewhat detailedexplanation of certain underlying mathematical principles that areinvolved. In Fig. l, the various shapes and forms taken by differentpieces of wire l through 9, of increasing springiness, in unwinding froma mam drel are shown. The piece of wire I represents a sample of wirewhich, hypo-thetically, is totally lacking in springiness. When thepiece of wire I is wound into circular form on a mandrel and the freeend is released, it will not unwind but will retain its completecontiguous circular form, as shown. The piece of wire 9 represents theother extreme. That is, the piece of wire 9 is a sample' of wire which,hypothetically, is 100% springy. When such a piece of rwire is woundinto circular form on a mandrel, and then released, it will straightenout into a perfectly straight line, as shown. The other pieces of wire2, 3, 4, 5, 6, 1, and 8 haveA various intermediate degrees ofspringiness or windability, in between these two extremes. That is, thepiece of wire 2 has very little springiness, while the piece of wire 8is much more springy. v

All of the pieces of wire l through 9 have the same equal length, andone end of each piece is held xed at the point, O, as shown. II thediameter of the circle outlined by the piece of wire l is d1, the lengthof this piece, as well as the lengths of each of the other pieces, willbe vr d1.

It has been found that each of the pieces of wire 2 to 8, will alwaystake the form ofv an arc of a circle.. As will be seen, the piece ofwire 2 is in the form of a nearly closed arc, of a relatively smallcircle, while the piece of wire 8 is in the form of an open are of acircle of large radius, and forms only a small portion ofthe entirecircumference of this larger` circle.

It has been found that the points P., or the free ends of the pieces ofWire, fall on a denite mathematical curve ill, shown in broken line. Themathematical equation for this-curve will be explained below. The curveif! may be divided or calibrated into various degrees of springiness,softness of windability. In this way, the softness and7 Winde-bility:properties ofany-sample of wire maybe determined by the locationtalrenby its free end on the curve liiias it unwindsl from acircular mandrel.'

The curve lili may be described as being the loci of points taken by thefree ends of circular `arcs-of constant length, and'increasing radii ofcurvature, all arcs having one end fixed at acommon origin andthecenters of thecircles ofwhich th'e1arcs:are a part all falling on astraight line throughV the common origin.

Inorder to derive the equation of 'curve i il, ref erence may be had toFigure 2 in whichv a circular arc of length L isf shown with one end atan origin or pole O and the free endat Pi This arc corresponds to, andis intended' to represent, oneof thepieces of wire, for example thepiece 8, in Figure-f1.v (As will be noted, the diagram of Fig. 2 isdrawn to a much smaller scale than the diagram of Fig. 1.) The origin Ocorresponds to the fixed end of the piece of wire while the point Pcorresponds to the free end of the piece of wire. The equation of theloci'offpoints P, or the free ends P of different pieces of wire 'tthrough 9, in Figure 1, may be derived as follows, employing the diagramof Figure- 2:

aa=L

where a is expressed in radians r=QP=2- a-sin (vr/2) =2(L/) sin (or/2)i=(1r/2) ox/2) However, since the length L of thev arc GP is constantandlequal to the circumference vrci oi' the initial circle, or themandrelon which the wireis wound', of` diameter. di, another form oftheequation is obtained by. putting Lzwdi:

T H sin H radius vector, and 0 is the vectorial angle. Substitutingdiierent values of 0 in the equation sin 0 0 0. 00 15 0. 92 30 1. 95 453. O7 60 4. 23 75 5. 38 6. 50 7. 50 l2() 8. 42 9. 25 9. 80 l0. 15 10. 20

When these values of 0 and 1' arek plotted, the curve l5l will beobtained, as shown in Fig. 3. It will be seen that this curve l5 is aVduplicate of the curve l 0in Figure l.

The above basic discussion and derivations-have been specificallyconcernedl with having one full turn of wire wound on a mandrel. It.hasbeen found in practice, however, that better results are obtained,when testing wire of certain sizes, if a number of turns of wire arewound onA the mandrel. The one-turn test is generally satisfactory fortesting copper wire in thelarger sizes, but :for sizes fromli down to 30A. W. GL, it is better to use` from Sito 5 turns onithe, mandrel.Whenwire-in these small sizesis tested, there inCr of the free endfromthel mandrel whenone is only a small amount of spring-back or unwindingof the freey end from the mandrel: when one turnis used. By using akplurality of turnsthe amount of springrback can be increased; Forexample, when five turns are used, the free end will spring backvsubstantia'liyve times as far as when only one turn is used; Thus, amoreaccurate indication oi the softness or Windability of the wiremay beobtained. Furthermore, when a number of turns are used and the pieces ofwire are correspondingly longer, a more representative sample of wire isthus tested than when a shorter piece is used. In addition, when anumber of turns of'wire are used, actual winding conditions are moreclosely approximatedthan when only one turn is used.

The Equationfz above is for oneturn of wire only. However, it has beenfound thatthe path or curvefollowed by the freeY end of; any number ofturns t1 of wire in unwinding froma mandrel .of diameter di may beexpressed by the following general equation:

iii is obtained by substituting 3 for the term t1 of Equation 3 above.Thus the Equation 4 of the curve I6 is:

7`= 'T Sill By substituting different values of @in the Equation 4., andtaking d1=1.8'75, a.v correspond.-

ing set of values of the length f the radius vector r may be obtained asfollows:

When this set of values of 6 and r are plotted, the curve I6 will beobtained, as shown in Fig. 4A.

The validity of the general Equation 3, the three-turn Equation 4, andthe curve it of Fig. 4A may be checked as shown in the diagram in Fig.4B. A circular mandrel il is shown having a diameter d1 with its centerat X. The vertical diameter of the mandrel Il intersects the top thereofat a point O, as shown. Assuming one end of a piece of wire is fastenedat O, and three complete turns are wound in a clockwise direc tion onthe mandrel Il, the points P taken by the free end of the wire inunwinding from the point O will be plotted.

It will be seen that when the wire has not unwound at all from themandrel Il', the free end will be at the point O where the fixed end isheld. Now, if the wire unwinds to any extent, the *free end will not beat O, but at some point P counterclockwise removed therefrom. However,although after unwinding there will not then be three complete turns ofwire, all of the turns of wire will lie in a circle of a larger diameterthan the diameter d1 of the mandrel il. The radius of any of theselarger or expanding circles formed by the wire in unwinding may bedesignated as m. It will also be seen that since one end of the wire isiixed at point O, the centers o these ex panding circles will lie atsome point Y on the vertical diameter of the mandrel and some distancebelow the center X thereof. The point O will be the end ofthe verticaldiameters of all of these expanding circles.

The length. of the piece of wire forming these expanding circles isconstant and equal to three times the circumference rch of the mandreli?. Letting y equal the angle between the vertical and the radius mdrawn between any free-end P of the wire and the center Y of itscorresponding expanding circle, it has been found that the length of theradius m may be expressed as follows: Y

(5) seo-l 2 By substituting various values of y in Equation 5, thecorresponding values of m may be obtained. For example, the length of aradius l0, Fig. 4B. where ly has a value of 60 and d1 has a value of1.875, may be obtained as follows:

The complete set of values of radii between values of y from 0 to 330where the mandrel Il has a diameter of 1.875 may be similarly calculatedand the lfollowing set of values obtained:

Each of the points P for each set o1 values is determined or located bylaying orf a Value of OY equal to the particular value of m. Forinstance, in the case of point P1, Fig. 4B, OY1 is laid off as 0.993.Then the radius mis is drawn out from Y1 at an angle of 60 from thevertical diameter, as shown in Fig. 4B. The point P1 is located bylaying off Y1P1 equal to OY1.

By repeating these steps, the other points P may be determined and theresulting curve 20 drawn therethrough. It will be seen that the curvesi6 of Fig. 4A and curve 20 of Fig. 4B are identical.

In the diagram of Fig. 4B, each of the expanding radii at the differentangles have been extended outside or beyond the curve 20, as shown.Since each of these extensions is an extension of a radius, each isthereby normal to the curve 20 at the intersections therewith.

These extensions or normals, e, form a scale by which the amount ofspring-back or uwinding of the free end P from the point O may bemeasured. Preferably, this scale is graduated in degrees of spring-backor unwinding per turn of wire. Thus, each of the Values of y will bedivided by a factor of 3. For example, the extension e1 of the radiusm18 having a value of 'y of 60 is marked as 20. The other extensions aresimilarly marked as 0, 10, 30, 40, 50, 60, 70, 80, 90, 100, and 110, asshown. It will be understood that intermediate graduations or divisio-nsmay be readily marked oil.

The discussion, procedure, and equations given above in connection withFigures 4A and 4B for three turns of wire in unwinding from a mandrel,are of `general application. Diagrams and scales, similar to those shownin Fig. 4B, may be developed for any number of turns of wire. TheEquation 5 may be generally expressed for any number of turns t1 as:

A curve for any number of turns of wire oorresponding to curve 20 ofFig. 4B, may be drawn, and a scale therefor may be graduated in terms ofdegrees of spring or unwinding of the free end per turn of wire on themandrel.

Although, normally scales and curves will be based on complete turns ofwire, it is obvious that they may be based on fractional turns such as21/2, 31/4, etc.

kReferring to Figs. 5, 6, and 7 of the drawings, a working embodiment ofmy invention in the form of a wire testing device is shown generally at25. The main body of the wire tester 25 consists of a casting whichcomprises a base 26 and an upright dish-shaped dial support '21, formedintegrally therewith. A central hub 28 projects from the inside 0f thesupport 2l. The front edgeof the hub 28 is plain and even with the rimor edge of the dial support 2. The rear of the dial support 21 is formedinto a thickened portion or bearing 29. A hole of uniform diameterextends through the hub 2S and bearing 29, as shown. The body of thetesting device 25 including the base support 25, dial support 21, hub29, and the rear bearing 29, may be made of cast aluminum, or any othersatisfactory material. It will be understood that the body of thetesting device 25 may be formed or built in other forms orconstructions.`v

A shaft 39 is journalled in the hub 28 and bearing 29, and projects atboth ends beyond these parts, as shown. In order to turn or rotate theshaft 355, a crank 3l is provided which fits over the right handprojecting end of the shaft and is keyed thereto by a pin 32. A smallthreaded hole is tapped through the top of the bearing portion 29, intowhich a thumb screw 33* is screwed. A shallow, flat recess Ell is cut inthe side of the shaft til into which the at end of the thumb screw 33fits, as shown. By tightening the thumb screw into the recess 3d, theshaft 39 may be locked or fixed in a predetermined position. When thethumb screw 33 is turned out or loosened, the lower end thereof will bewithdrawn from loci/:ing engagement with the recess 35i and the shaftIt@ may be rotated by turning the crank 3i.

A two-diameter mandrel member E35 with a central hub fits over the lefthand projecting end of the shaft 3ft. rIhe mandrel member 35 may befastened in any desired position on the shaft 3G by a set screw 3l'. Themandrel member 35 includes a small diameter mandrel lili, and largerdiameter mandrel lL Angularly holes [if and areformed or drilled throughthe mandrel surfaces, as shown. The holes 4E and "i3 are provided sothat the ends of pieces of wire being tested may be inserted therein andthus retained on the mandrel, as will appear hereinafter. The rear orback edge of the small mandrel to and the front edge of the largermandrel di are connected by an integral, annular wall ll having a planeannular outer or front surface.

In the particular embodiment of my invention shown, the mandrel @il isintended to be used in testing three turns of wire. Accordingly, anannular dial d5 and Celluloid protecting member M5 are slipped over thesmall mandrel All and fastened to the annular mandrel connecting walllld'by four screws Ill (Fig. 5). Referring particularly to Fig. 5 of thedrawings, it will be seen that scale 45 of the dial comprises a curve29' which corresponds to the curve it in Fig. 4A, and the curve 2li inFig. 4B. The scale of the dial 45 is graduated in degrees of spring-backor unwinding per turn, and the zero mark of the scale is angularlyaligned with the small hole flZ in the Inandrel lli), as shown. It willbe seen that the small mandrel till, the large mandrel di, and the scale.15 rotate as a unit when the shaft 39 is turned.

The larger diameter mandrel l is adapted to be used for testing samplepieces of wire in five turns thereon. Accordingly, a dial 5t is made,which is calibrated in degrees of spring-back or unwinding per turn onthe mandrel lll. The dial 50 (Fig. 5) has a curve 5l drawn thereon whichcorresponds to the curve 29 on the dial 45. However, it will be notedthat the curve 5l is not the same shape as the curve 29', since it isdeveloped for five turns instead of for three. The graduations for thedial 59 comprise normals to the curve 5I as shown. The dial 59 is placedbetween an annular metal plate 52 and an annular Celluloid cover 53, andthis assembly is held or fastened to the front edge of the dial support21 by screws 54, as shown in Fig. 6. The zero mark of the dialEsisangularly aligned with the vertical diameter of the dial support 21.It will be seen that the mandrel 4I is rotated inside of the annularscale 59; The mandrel member 35 is so set on the shaft 30 that when theshaft is locked in position bythe thumb screw 33, the zero marks of thescales 45 and 5U will be angularly aligned, as well as the small holes42 and t3 in the surfaces of the large and small mandrels l5 and 4l.

Although it will be understood that wire testing devices embodying myinvention may be made in different dimensions and sizes, I have foundthat for most testing purposes satisfactory results are obtained whenthe small mandrel il has a diameter of 1% inches, and the large mandrel4I has a diameter of 3% inches.

Wire in sizes of 30 down to 21 A. W. G. is satisfactorily tested on thesmall mandrel 40, while larger wire in sizes of 20 to 14 A. W. G. may besatisfactorily tested on the larger mandrel 4l.

The technique of testing samples of wire on the wire tester 25, and theoperation thereof, will be described in connection with Figs. 8 and 9 ofthe drawings. For purposes of explanation, the technique will bedescribed in connection with testing a sample piece of wire of liveturns on the larger mandrel lil. Referring to Fig. 8, a piece of wireiii?, shown in broken lines, is unwound from a reel of wire 5l in themanner shown. The end of the wire 5t is brought aroundthe right side ofthe large mandrel 4I and inserted in the hole 43 in the top thereof. Thepiece of wire 69 is now cut at the point indicated by the cross 52 and aonepound weight 63 fastened thereto, as shown. The thumb screw 33 is nowunturned so that the shaft 3i! and mandrel member 35 may be turned bythe crank 3 l. After iive complete turns of wire have been wound in aclockwise direction on the mandrel lll, the testing device 25 is lockedby turning down the thumb screw 33. The piece of wire 6d is now cut sothat a free end 64 may be turned up at the zero graduation as shown inFig. 9.

Now in order to test the softness or windability of the piece of wire69, a pencil or stylus 65 is used to hold the free end 64 in place asshown in Fig. 9. The stylus 65 is slowly moved counterclockwise aroundthe scale of the dial 5l), as indicated, with the free wire end 64following it until the free end 64 will spring back or unwind nofurther. By way of illustration, the free end is shown in Fig. 9 inbroken line as having sprung back to the 30 mark or graduation of thescale` 59. Hence, the piece of wire 6l) may be said to have awindability or softness of .30 per turn.

Different sized weights, corresponding to the weight till, are used intesting wire of different sizes on different sized mandrels. Thefollowing table to be used in connection with testing sample pieces ofwires on the wire testing device 25, having the particular dimensions asspecified above, has been found tov be satisfactory. l

The method of testing wire described, and the wire testing device 25 aresuitable for both laboratory and production tests. Very uniform andaccurate results may be obtained by an operator after relatively littleexperience and instruction.

An actual illustration may be used to show the important advantages ofmy invention. A #18 A. W. G. bare copper wire annealed at 900 F. willproduce an extremely soft Wire. It will, however, exhibit some tendencyto spring. When a sample of such a Wire was tested according to themethod, and on the testing device of my invention, using a 31A" mandrelwith a one pound tensioning weight and ve turns, this wire showed aspring-back at 24 per turn.

When this same Wire was annealed at 750 and similarly tested, accordingto my invention, it showed a spring-back of 33 per turn. This was anincrease in springiness of 9 per turn. However, vvhen these two wireswere tested by the percent of elongation method normally used fordetermining comparative softness, they were classiiied as being alike,or at least very close together.

The application of insulation to a bare Wire imparts an additionalhardness or springiness to the wire, due partly to the stiiening elfectof the insulation and partly to the work hardening of the Wire due tobending during processing. The sample of #18 A. W. G. wire, annealed at750 F., previously referred to as having a spring-back of 33 per turn,had a percent elongation of 40% when bare. When this piece of Wire wasinsulated with an enamel coating, it exhibited a loss of from 1 to 2% ofthe elongation. However, the windability or springiness increased to 51per turn as tested according to my invention. Thus where the percentelongation test showed only a slight change, my test indicated anincrease in springiness of 18 per turn.

From this discussion of actual comparative tests, it is obvious thatmore accurate indications of the actual softness cf wire for windingpurposes may be obtained according to the method and apparatus of myinvention.

From a large number of tests, it has been established that my foregoingmethod and apparatus of testing the softness of Wire for windability hasthe following advantages:

1. It is an accurate check on the actual Windability of wire.

2. The results can be duplicated readily and by different operators.

3. The testing device is suitable for laboratory, as well as shop andinspection department requirements.

4. Test samples are suilciently large to give averaging results, and areless affected by the initialed curvature of the wire imparted by thereel or coil.

5. The time required to make the tests is not greater (is equal lorless) than that required for practicing existing methods.

6. The testing device or apparatus is rugged, simple, and of inexpensiveconstruction.

It will be seen that certain changes and modications may be made in thetechnique of using, and the construction of wire testing apparatus of,my invention. However, the broad underlying principles and features willremain the same. Accordingly, it is intended that all matter shown inthe accompanying drawings or described hereinbefore shall be interpretedas illustrative only and not in a limiting sense.

I claim:

1. A device for testing the softness or windability of wire comprising,in combination, a cylindrical mandrel, a shaft supporting said mandrel,journal support means for said shaft providing rotatable movement ofsaid mandrel, means for retaining one end of a piece of wire beingtested at a point on said mandrel, a dial, means supporting said dial,adjacent said mandrel in cooperative relationshipr therewith, thegraduations of said dial comprising normals to a curve the equation ofwhich in polar coordinates where 1' is the radius vector, 0 is thevectorial angle in radians, t1 is the number of turns of wire wound onsaid mandrel, and d1 is the diameter of the mandrel, said mandrel andsaid dial being so disposed relative to each other that said point onsaid mandrel Where one end of the wire being tested is retained isrotatable into angular coincidence with the origin of said curve, saiddial being calibrated in degrees of spring-back or unwinding per turn ofwire on the mandrel, and stop means for locking said mandrel againstmovement relative to said dial when the point at which said Wire is heldon said mandrel is in angular coincidence with the origin of said curve;

2. A device for measuring the windability or softness of wirecomprising, in combination, a support body; a hub projecting from saidsupport body; a shaft journaled in said hub and projecting therefrom; asmall and narrow mandrel mounted on said shaft and adapted to have anumber of turns of small size Wire wound thereon, a small hole beingprovided in the surface 0f the small mandrel in which one end of a pieceof Wire wound thereon may be held; a dial movably mounted with saidmandrel and iitting therearound; the graduations of said dial comprisingnormals to a curve the equation of which expressed in Ipolar coordinatesis =$L0 sin 0 where r is the radius vector, 0 is the vectorial yangleexpressed in radians, t1 is the number of turns of wire Wound on saidsmall mandrel, and d1 is the diameter of said small mandrel, the originof said curve coinciding in angular alignment with said small hole inthe mandrel surface, and said dial being calibrated in degrees ofspring-back or unwinding per turn of wire on the small mandrel; a largermandrel mounted on said shaft and adapted to have a number of turns oflarger size wire wound thereon, a small hole being provided in thesurface of the larger mandrel in which one end of a piece of wire woundthereon may be held; and a fixed dial fitting around said larger mandreland supported on said support body; the graduations of said xed dialcomprising normals to a curve the equation of which expressed in polarcoordinates is sin 0 r=$2 sin 0 Where r is the radius vector, 6 is thevectorial angle in radians, t2 is the number of turns of wire Wound onsaid larger mandrel, and d2 is the diameter of said larger mandrel, saidlarger mandrel being rotatable so that said small hole in the surfacethereof may be angularly aligned with the origin of the graduation curveof said fixed dial, and said fixed dial being calibrated in degrees ofspring-back or unwinding per turn of Wire Wound on said larger mandrel.

3. A device for measuring the Windability or softness of Wirecomprising, Yin combination; a support base; a dish-shaped supportmember carried on said support base; a central hub projecting from thecenter of said dish-shaped support member with the opening in the hubpassing through the rear of the dish member; a shaft journaled in saidhub and projecting beyond the rim of said dish-shaped support member; acrank connected to the rear end of said shaft for turning the same; amulti-diameter mandrel member centrally mounted on the projecting end ofsaid shaft having a small diameter mandrel and a larger diameter mandrelWith a plane annular Wall between the-outer edge of the larger mandreland the inner 4edge of the smaller mandrel, and small angularly alignedholes provided in the surfaces of the small and larger mandrels wherebythe ends of pieces of Wire may be inserted and held; a Adial -for saidsmall mandrel mounted on said plane annular wall and rotatable With saidmulti-diameter mandrel'member, the graduations of said `dial comprisingnormals to a curve the equation or" which expressedin polar coordinatesis Wherey r is the radius vector,'0 is the vectorial-angle in radians,t1 isthe number of turns of Wire Wound on said small mandrel in testingthereon, and d1 is the diameter of said small mandrel, the origin orpole of said dial graduation curve coinciding in angular yalignment withthe small Wire hole in the small mandrel, andisaid dial being calibratedin degrees 'of spring-hacker unwinding per turn `of wire wound on `thesmall'mandrel; a stationary dial for Vsaid larger mandrel tting aroundthe backthereof and fastened to the rim of said dish-shaped supportmember, the graduations of said stationary dial comprising normals to acurve the equation of which expressed in polar coordinates is Wire woundon the larger mandrel in testing sin thereon, and d2 is the diameter .ofthe larger mandrel, said larger mandrel lbeing rotatableso that the wirehole in thesurface thereof' may lbe angularly .aligned with the yoriginor pole of the graduation curve of said stationary .dial for the largermandrel,A and said `stationary dial being calibrated in degrees ofspring-baok or unwinding per turn of Wire Wou-nd Aon ksaid largermandrel; and stop means for locking .saidmulti-diameter mandrel. memberin `angular relationship with the stationary dial. for thelargerlmandrell fl. In combination :in Va device for measuring theWindability or ,softness of Wire, a mandrel which comprises twoconcentriccylindrical sections of differing diameters disposedlongitudinaily adj acent each other, means supporting said mandrel forrotative movement including a supporting shaft, k,a stationary supportmember in which said shaft is journaledfand .a crank'for rotating saidshaft `and mandrel, .angularly aligned holes being provided in thesurface of each section'of said mandrel, each of said holes beingadapted'to receive and hold one end of a piece of Wire to be tested, ascale for said smaller mandrel section supported on 'and rotatable Withsaid larger mandrel section, and a scale for said larger mandrelvsection xedly mounted Von said stationary mandrel support means, thegraduations on each of `said scales comprising normals to a curve theequation of 'which expressed in polar coordinates is Tdt Tlf-0 Where ris the radius vector, y6 is the vectorial angle in radians, t is theynumber of turns of wire Wound on saidmandrel section, and 'd is .the:di ameter of said mandrel section, said `scaleszbeing calibratedinodegrees of-spring back or-un- Winding per turn of Wire von theassociated mandrel section, the `origin of the curve on the scale forthe smaller mandrel section coinciding in angular alignment with thesaid 'hole in said smaller mandrel section, the said hole inthelargermandrel section being inangular alignment lwith the origin of thecurve on the scale for the `larger mandrel section vvhen said rmandrelis rotated into a predetermined posi-tion, `and stop means for lockingsaid mandrel in said predetermined position during the use of saidlarger mandrel. RAYMOND L. READING.

sin 6 CERTIFICATE' 0E coRREcToE. Pai-.ent No. 2,558,202- January 1L,19M-L.r

RAYMOND L. READING.

ItA is hereby certified 'that error appears in the printed specificationof tbe above numbered patent requiring correction as follows: Page 2,fir-st column, line 2l, for "of"4 read -or-; and second column, -line 6,before where insert an opening parenthesis; line 5'?, strike out thesyllable and Words ing of the free end from the mandrel when one"; page6, second column, line 50claim lA, after "mandrel" insert -section; andthat the said Letters Patent should be read with 'this correctiontherein that the same may conf orm to the record of the case in thePatent Office.

signed and Sealed this 13th day of April, A. D. 1914A.

Leslie Frazer (Seal) Acting Commissioner of Patents.

